Various contactless power supplying systems that use contactless power supplying techniques have been proposed over these recent years. In particular, contactless power supplying systems that use electromagnetic induction have become practical.
In an electromagnetic contactless power supplying system, a contactless power supplying device includes a plurality of primary coils arranged in parallel to a setting surface on which an electric appliance is set. The electric appliance, which is supplied with power in a contactless manner from the contactless power supplying device, includes a power reception device. A secondary coil is arranged in the power reception device.
In Japanese Patent No. 4639773, when the electric appliance is set on the setting surface of the contactless power supplying device, among the primary coils arranged in the contactless power supplying device, the primary coil opposing the secondary coil, which is arranged in a power reception device of the electric appliance, is selected. The selected primary coil is excited and driven to supply the secondary coil with secondary power.
In the contactless power supplying device of Japanese Patent No. 4639773, a single oscillation circuit (resonance circuit) is used to drive the primary coils. The resonance circuit is connected to each primary coil to excite and drive the primary coil. Accordingly, the excitation frequency is the same for each primary coil.